How long is DNA?

The DNA in a single human cell is about 2 meters long when you uncoil it and lay it out straight. That sounds impossible for something sealed inside a nucleus only 6 micrometers wide, but it is true, and it is only the beginning. Multiply that 2 meters across the trillions of cells in your body and the total length becomes genuinely astronomical: somewhere between 6.2 and 14.4 billion kilometers, depending on how you count your cells.

The precise per-cell figure is 2.06 meters for a human diploid genome, derived from chromosome-scale sequence lengths. This guide works through where that number comes from, how the body folds 2 meters of thread into a microscopic space, and what the length looks like for a single chromosome, a single gene, and the whole human body.

How long is DNA in a single human cell?

A single human diploid cell contains about 2.06 meters of DNA. More precisely, it measures 205.00 cm in males and 208.23 cm in females, with a reported mean of 206.62 cm.[1]On the length, weight and GC content of the human genomeBMC Research Notes · 2019View source

Those values come from a 2019 analysis of chromosome lengths in the male and female diploid human genome. The female genome is slightly longer because the second X chromosome is longer than the Y chromosome.

The math behind it is simple. A diploid cell holds about 6.3 billion base pairs, and each base pair adds 0.34 nm of length along the helix. Multiply the two and you get roughly 2.1 meters per cell.

How long would all your DNA be stretched out?

Stretched end to end, all the DNA in one person reaches roughly 6.2 to 14.4 billion kilometers, enough to make about 20 to 48 round trips between Earth and the Sun (the Sun sits about 150 million km away).

The range exists because the total is a derived estimate, not something anyone measures directly, and it depends almost entirely on how many nucleated cells you assume. Using the 2023 whole-body cell census, a 70-kg reference male contains about 36 trillion total cells, of which about 29 trillion are nonnucleated blood cells. That leaves roughly 7 trillion nucleated cells, each carrying a full copy of the genome.[2]The human cell count and size distributionProceedings of the National Academy of Sciences · 2023View source

Combine those 7 trillion nucleated cells with the 2019 diploid male genome length of 205.00 cm per cell and the body holds about 14.4 billion km of nuclear DNA. That is larger than the widely repeated 6.20 billion km figure, which came from pairing a similar per-cell length with an older assumption of 3 x 10¹² nucleated cells.[1]On the length, weight and GC content of the human genomeBMC Research Notes · 2019View source[2]The human cell count and size distributionProceedings of the National Academy of Sciences · 2023View source

Put another way, the DNA in a single body is longer than the distance from the Sun out to Pluto. Scale it up once more and the numbers leave the Solar System entirely: across all ~8 billion people alive today, human DNA adds up to somewhere between 5 and 12 million light-years of thread, several times the distance to the Andromeda Galaxy. Every meter of it is folded into spaces too small to see.

How does 2 meters of DNA fit inside a cell?

The cell fits 2 meters of DNA into a 6-micrometer nucleus through several nested layers of coiling, the rough equivalent of packing about 20 kilometers (12 miles) of thread into a tennis ball.[6]DNA Packaging: Nucleosomes and ChromatinNature Education · 2008View source

It happens in stages:

• Nucleosomes: the double helix wraps roughly twice around clusters of proteins called histones, like thread around a spool. This is the first and most important level of compaction.
• Chromatin: those nucleosome spools coil together into a denser fiber.
• Chromosomes: during cell division the fiber condenses thousands of times further into the compact, X-shaped chromosomes you see under a microscope.

This packing is also why DNA is invisible to the naked eye even though a single cell holds more than your body's height in genetic material.

How long is a single chromosome?

A single human chromosome, fully uncoiled, measures about 1.5 to 8.5 cm. The largest, chromosome 1 (about 249 million base pairs), stretches to roughly 8.5 cm, while the smallest, chromosome 21 (about 47 million base pairs), is only about 1.6 cm.[7]Genome Reference Consortium Human Build 38 (GRCh38) assembly statisticsNCBI Genome Data ViewerView source

A common point of confusion is whether DNA is "smaller" than a chromosome. They are the same material. A chromosome is simply one continuous DNA molecule wound up with packaging proteins, so the difference is not size but how tightly the same strand is coiled. Add the DNA from all 46 chromosomes together and you arrive back at the roughly 2 meters per cell.

How wide is DNA?

The DNA double helix is only about 2 nanometers wide, roughly 40,000 times thinner than a human hair. Along its length, each base pair adds 0.34 nm of rise.[4]Three-dimensional positioning and structure of chromosomes in a human prophase nucleusScientific Reports · 2017View source

That extreme thinness is exactly why 2 meters of DNA can fit inside a cell at all. The smallest structural unit, a single base pair (two paired nucleotides), is what every length figure in this guide is built from.

How long is a single gene?

Genes are short stretches of the same DNA strand, and they vary enormously. An average human protein-coding gene spans on the order of 10,000 to 30,000 base pairs, which works out to about 3.4 to 10 micrometers of DNA when uncoiled. The largest known human gene, dystrophin (DMD), runs about 2.4 million base pairs, roughly 0.8 mm of DNA for a single gene.

Despite their length, genes that code for proteins make up only a small fraction of the genome. For how those stretches are counted and organized, see our guide on how many genes humans have.

How long is human mitochondrial DNA?

The human mitochondrial genome contains 16,569 base pairs. Multiply that by 0.34 nm per base pair and one fully extended mitochondrial DNA molecule is about 5.6 μm long.[3]The little big genome: the organization of mitochondrial DNAFrontiers in BioscienceView source

That is tiny compared with nuclear DNA. Even though a typical cell carries on the order of 1,000 mitochondrial genome copies, the total mtDNA length adds up to only a few millimeters per cell, not meters.[3]The little big genome: the organization of mitochondrial DNAFrontiers in BioscienceView source

Which organism has the longest DNA?

The record-holder is the New Caledonian fork fern Tmesipteris oblanceolata. A 2024 study reported a genome size of 160.45 Gbp/1C, surpassing the previous record-holder Paris japonica at 148.89 Gbp/1C.[5]A 160 Gbp fork fern genome shatters size record for eukaryotesiScience · 2024View source

Converted to diploid cell lengths at 0.34 nm per base pair, those genomes correspond to about 109 meters of DNA per cell for Tmesipteris oblanceolata and about 101 meters for Paris japonica. That puts the human diploid genome, at about 2.06 meters, far below the upper end of known eukaryotic genome lengths.

Methodology

This article uses a mix of figures reported directly in the literature and figures derived from those reported values. The per-cell lengths of 205.00 cm, 208.23 cm, and 206.62 cm for the male, female, and mean human diploid genome are reported directly in D'Onofrio et al., as is the 6.20 billion km whole-body total, which assumes 3 x 10¹² nucleated cells.[1]On the length, weight and GC content of the human genomeBMC Research Notes · 2019View source The larger 14.4 billion km whole-body figure is a derived estimate that pairs the 205.00 cm male per-cell length with the roughly 7 x 10¹² nucleated cells implied by the 2023 reference-male cell census, giving about 1.44 x 10¹³ meters.[1]On the length, weight and GC content of the human genomeBMC Research Notes · 2019View source[2]The human cell count and size distributionProceedings of the National Academy of Sciences · 2023View source The round-trips-to-the-Sun and light-year comparisons apply an Earth-Sun distance of 150 million km and a light-year of 9.46 trillion km to the whole-body and roughly 8 billion person totals.

The remaining lengths follow the same conversion of base pairs to physical length at 0.34 nm per base pair. The per-chromosome figures (8.5 cm for chromosome 1, 1.6 cm for chromosome 21) come from GRCh38 chromosome base-pair counts.[7]Genome Reference Consortium Human Build 38 (GRCh38) assembly statisticsNCBI Genome Data ViewerView source The 5.6 μm mitochondrial length follows from 16,569 bp x 0.34 nm per bp, which equals 5,633.46 nm.[3]The little big genome: the organization of mitochondrial DNAFrontiers in BioscienceView source The 109 m and 101 m plant-cell comparisons are derived from reported 1C genome sizes, assuming diploid 2C nuclei before converting to length.[5]A 160 Gbp fork fern genome shatters size record for eukaryotesiScience · 2024View source

Matic Broz

Founder & CEO, ProteinIQ

Matic founded ProteinIQ to make computational biology accessible to every researcher. He builds code-free bioinformatics tools used by thousands of scientists worldwide for protein analysis, molecular docking, and drug discovery.